This invention relates to a hand drilling apparatus and more particularly comprises a new and improved dental drill which operates in the intermediate to high rotating speed range.
The development of carbide and diamond drill bits and adequate cooling systems for them has been accompanied by the development of high speed dental drills, as typified in Page U.S. Pat. No. 2,824,370, dated Feb. 25, 1958, and Hoffmeister et al. U.S. Pat. No. 3,092,908, dated June 11, 1963. These patents illustrate the two major approaches taken in the development of high speed drills. In the Page device the handpiece is connected to and driven by a conventional engine arm, and the high speed is attained through the step up of pulley sizes in the handpiece. The high speed drill of Hoffmeister et al. employs an air turbine directly connected to the drill chuck and driven by compressed air directed from a source through a duct in the handpiece.
The air turbine type handpiece although light and maneverable because it is only connected by one or a few very flexible hoses to the compressed air source and perhaps a water supply for cooling, nevertheless is useful only in the highest speed ranges where the tactile control is extremely light. Small increases of pressure stall this instrument unpredictably, and if the instrument is operated at lower speeds at reduced air pressures, the instrument stalls even more easily. On the other hand, the more conventional types of dental engines and engine arm drives have enough power and torque to maintain tooth grinding and cutting operations at more moderate speeds where tactile pressures are proportionately greater. However, these handpieces are relatively heavy and awkward because of the connections to the engine arm. Further, the weight, vibration and inertia of parts attached to such handpieces during brush-like strokes against the teeth reduce the operator's sensitivity.
Most dentists prefer one or the other type of dental drill and have equipped their offices accordingly, but many dentists have both so as to be able to use instruments best suited to perform the particular operation at hand. This solution has many obvious disadvantages, not the least of which is the double expenditure involved.
It is a general object of this invention to provide an improved dental drilling instrument capable of operating at a speed and power which may be selectively varied by the operator in a closely controlled manner.
Another general object of this invention is to provide a lighter, more flexible and more maneuverable dental drill than those now available having a high degree of controllability and sufficient power.
Yet another object of this invention is to provide a dental drill which affords the operator optimum control throughout the intermediate to high rotating speed range so as to increase the number of easily performable operations by use of a single piece of equipment.
Still another important object of this invention is to provide a mobile and easily transportable dental drill which does not require a conventional dental console or large compressor but only a standard A-C outlet.
A further object of this invention is to provide electric high speed dental and surgical drills which may be used safely in the presence of explosive and combustible mixtures of gases that are present when certain general anesthetics are used.